This invention relates to aluminum alloys. More particularly, this invention relates to aluminum base, low-melting temperature alloys for utilization in joining titanium structural elements through a conventional brazing process.
The process of brazing is a type of welding technique used for joining together metal elements through the use of a nonferrous filler, or brazing material, which has a lower melting point than the metal elements being joined. The filler material, or brazing alloy, is distributed in its molten state between the adjoining surfaces of two metal members by capillary action. The selected brazing alloy must "wet" the abutting surfaces or in other words, adhere to the surfaces by alloying and diffusion. Generally, the melting point of the alloy is around 800.degree. F or higher. The high melting point and great strength achieved in the brazing process differentiates it from soldering.
The brazing process varies widely in technique and is utilized in many industrial appllications for joining metal surfaces in the fabrication of structural elements. The recently increased research effort in the development of high speed and high altitude aircraft has produced greater interest in the use of brazing processes. Such aircraft encounter severe stresses and strains during operation resulting in the need for light weight construction materials of considerable strength. Sandwich type construction panels have proven extremely useful in providing the necessary high strength to low weight ratios needed for these high speed aircraft.
However, problems are often encountered when using titanium metal as the structural material for the sandwich type elements. The joining together of one titanium surface to another does not produce the high strength bond needed under severe conditions of stress and strain, especially at elevated temperatures. In attempting to solve the problem of joining titanium surfaces with a high strength bond, it has been found that an aluminum base brazing alloy of the type contemplated by this invention provides a solution by effectively joining the surfaces with a high strength bond without degrading the basic titanium metal due to the use of the high melting brazing alloys relied on in the past.